This invention relates to lens systems for optoelectronic transducers.
In some optoelectronic device situations, an array of optoelectronic transducers is required. Further, in some of these situations, a lens must be provided for each of these optoelectronic transducing devices to properly direct the transmitted electromagnetic radiation interacting with these devices.
These optoelectronic transducers typically have structural features which are usually on the order of microns, and almost always less than a mil. There are substantial difficulties in providing similarly sized lenses of good quality. Such lenses usually require techniques different from those used in providing ordinary lenses. One such technique is to take a previously formed glass sphere and mechanically position and hold the sphere adjacent to the transducer such that the sphere itself serves as a lens. Another technique is to fabricate a lens right on the transducer itself, as shown in U.S. Pat. No. 4,058,821 to Miyoshi, et al. This reference shows the placing of a selected amount of glass on a portion of a material layer already provided over a semiconductor photodetector and then heating the selected amount of glass to its melting temperature. This glass, after melting, flows over the material layer and, through surface tension, takes the shape of a lens which it maintains after cooling below the melting temperature. However, raising the amount of glass to its melting temperature also requires heating the semiconductor device which may be detrimental to the structures, including those forming circuit components, contained therein. Further, making several lenses for each chip, and doing so for chip after chip, can be prohibitive in large volumes.